Fire alarm



Dec. l5, 1959 G. T. K. DURLAND 2,917,606 a FIRE ALARM Filed lay 14, 1956 if: A ram/5x2 United States Patent O FIRE ALARM Gen'et T. K. Durland, Noroton Heights, Conn., assgnor to Unique Balance Co., Stamford,-Conn., a corporation of Illinois Application May 14, 1956, Serial No. 584,508

6 Claims. (Cl. 200-142) 'ing devices are well known articles vof commerce. De-

vices comprising resilient contact means normally spaced apart "by 'a heat-fusible material have taken many forms. These Vmechanisms have, however, been generally fairly complex `and have been too large and yexpensive to be readily adapted for use in homes and vthe like.

'It is "an object of 'this invention, therefore, to ,provide a lire alarmsystem which, because of its inexpensive .and simple nature, can be employed in homes, apartments and 'individual rooms as well Ias in .larger buildings and commercial establishments.

.Afurtherobject of 'this invention is to provide aheat detecting circuit closing device for use yin-a lire alarm -system which may be readily manufactured by low-cost m'ass `production methods.

Another object of this invention s to provide are detectingdevice'for use in a fire alarm system which is 'ofvery small size and which, at the same time, is eX- treme'ly sensitive to temperature increases in the air "currents contacting its surface.

Still another object of thisrinvention is tofprovide a .fre 'alarm system including "both visible and audible alarm means, which system is simple and Vpositive in operation 'and inexpensiveto installand maintain.

.These and other objects of the invention are realized "bypr'oviding'an'automatic fire alarm4 system comprising "an electrical circuit, oneor a ,plurality of lire-detecting units connected in parallel with the circuit, an audible alarm, one ora. plurality of signallamps andXed resistors inithe circuit between each detecting device and the alarm, and' a1 power source.

Each detector unit comprises a tube of nonconducting 'material and a'p'air of `contact -elements lfrictiona'llyposiy'tioned within`the'tu`be. 'The contact elementsare connected to a 'corresponding conductor of the circuitand .are spaced apartby an insulating member. The-ends ofi` each conducting element remote "from the conductor f'formconta'ct'iarms'whch are normally urged together. The contact arms, however, are normally spaced apart by a heat-fusible element, thus maintaining an open circuit.

These and other advantages of the present invention will become evident in the discussion of the accompanying drawings in which:

Figure l is a perspective view showing the re detector unit of the present invention;

Figure 2 is an end elevation of the detector unit shown in Figure l;

Figure 3 is a longitudinal cross-sectional view of the device of Figure 2, taken along the view lines 3--3 looking in the direction of the arrows; and

Figure 4 is a schematic drawing showing a suitable 4a low -voltage lamp `30,

arrangement of circuits for the lire alarm system of this invention.

Referring now to the system shown by Figure 4, a power source 10 is connected by means of a conductor 11 to a plurality of conductors 12 leading to a plurality of detector devices 13. Each detector device 13 comprises a pair of conducting elements 14 and 15 arranged within a tube 16 of an insulating material.

The conducting elements 14 and V15 shown in detail in Figures 1 and 3 are of a resilient electricity-conducting material such as Phosphor bronze, and are preferably in the form of strips, containing free ends 17 and 18, substantially centrally located constricted portions 19 land 20, bowed portions 21 and `22 and contact arms 23 and 24.

The conductor 12 bringing electrical energy from the power source 10 is connected to the free end 17 ,of the conducting element 14. The conducting elements 14 and 15 are kspaced apartat the constricted portions 19 and 20 by means of an insulator 25. The freeends 17 and 18 are biased in the direction of the confining walls of the tube 13 and are in frictional engagement therewith. The constrictedportions 19 and 20 with the intermediate insulator 25 are retained .in a properly aligned relationship by means of a winding 26 of insulatingfmaterial.

The bowed portions 21 and 22 are pinched together prior to `their insertion into the `tube 13,.and are there- Vfore urged in the direction of the retaining walls of the tube 13 to'form a frietional engagementtherewith. ',Because of the compression of the bowed portions 21and 22, lthey also urge the contact arms '23 and 24 'in the direction of their normally closed position. The Contact arms 2-3 and 24vare spaced apart, however, bymeans of a heat-fusible element 27. n

Referring again to Figure 4, the ,conductor 28.,.leads from thefree end 1-8 of conducting element 15 to aiixed resistor 29. A lead 29a connects the conductor 28 with while a lead 29b connects the lamp 30 with a conductor 32, A test switch 31 is inserted to bridge the gap in the circuit between the conductor 28 and the conductor 12. The conductor 32 leads from the fixed resistor .29 to an alarm 33. A n Vadditional conductorv34 leads from the alarm 33 tothe power source 10. --Referring again to Figures 1 and 3, thefree end` por- 'tlon 18 of `.the conducting element 15 contains an-area 34 where the conductor 28 is attached by means'of-Solder. A lanced portion 35 isformedby pressing out.aportion of ,contact element 14.in the form of `a point/the point being directed toward theopposing conducting element `15. A formed pocket 3,6 at the tip of each of thecontact arms 23 and 24 secures the fusible element 27 in position. Acoating 37 ofinsulating-material is ,provided within thepocket 36 to prevent passage of electric current from. the contact arm-2310 the Vcontact arm .4:24 in the event. the `fusible .element 2,7 is ofgaaonductingv materia The lire detector unit 13 may be disassembled and assembled with relative ease. As the conducting elements 14 and 15 are retained within the tube 16 solely by means of frictional engagement, the tube may be readily slipped oif from the conducting elements 14 and 15. When the elements 14 and 15 are removed, the winding 19 maintains the elements 14 and 15 in their opposed relation at their centrally constricted point, but the tension is removed. The fusible plug 27 falls free.

In order to re-insert the elements 14 and 15 into the tube 16, it is only necessary to replace the fusible plug 27 at its proper place between the contact arms 23 and 24, compress the resilient contact members 14 and 15 so that they may be readily received within the tube 16, and slide the tube into position over the contact elements 14 and 15. Confinement of the contact elements 14 and 15 within the tube in this manner provides a means of frictional anchorage and also creates a powerful inherent source of mechanical energy for closing the contact arms.

It will be readily seen that the detector devices 13 of this invention may be easily attached at the desired site by means of attaching the tube 16 to a wall or other desired place. The tube 16 may be transparent, but is preferably made in decorator colors to harmoniously blend in with interior moldings or other decorative features.

The tube 16 may be either compression molded of any suitable plastic or other insulating material, or it may be cut olf from tubular extrusions of similar material.

Any number of the detector units with appropriate circuits may be added to a lire alarm system without adversely affecting its eciency in any way. As the portion of the contact arms 23 and 24 engaging the fusible plug 27 extends slightly from the tube 16, the device is more sensitive to temperature changes in the surrounding air. When the temperature of convected air currents reaches the yield point or melting point of the fusible plug, the plug collapses, allowing the contact arms to close. Where a lanced contact point 35 is employed, the point is forced into contact with the opposing conducting element to close the circuit, thereby energizing the alarm and indicating the presence of a fire.

The fusible plug 27 may, of course, be of any desired material and where a metallic alloy having the desired melting point is employed, it is advantageous that the contact arms 23 and 24 immediately adjacent the fusible plug 2.7` be insulated in order to prevent passage of current through the metallic plug. Other materials, however, such as suitable waxes, may be employed as a heatfusible plug where desired. The plug may easily be replaced with higher or lower melting materials, according to changes in local lire hazards. It is also noted that the location of the contact point within the protective covering of the tube 16 lessens the danger of covering the contact points with dust, paint, grease and the like, which would tend to prevent proper closing of the contact points.

The test switches 31 are provided in the event periodic testing of the power source 10, signal lamp 30 and alarm 33 is desired.

It will be understood that the above-described embodiment of the invention is illustrative only and that modiications will occur to those skilled in the art. Accordingly, the invention is not to be limited to the specific apparatus disclosed herein, but is to be defined by the appended claims.

I claim:

1. In an electrically energized fire alarm system a heat-responsive circuit-closing detector unit comprising, a casing of non-conducting material, a pair of resilient conducting elements received within the casing, and a solid, heat-fusible plug, each conducting element having a free end, an inwardly constricted portion, a bowed portion and a contact arm, the solid heat-fusible plug separating the contact arms of the conducting elements and the resilient contact arms being spaced apart within the casing lat the inwardly constricted portion by an insulator, the conducting elements being arranged to cooperate with each other and with the inner surfaces of the casing in such a manner that the conducting elements are compressed and urged into frictional engagement with the inner surfaces of the casing to frictionally anchor the elements within the casing and to normally urge the contact arms to a closed position.

2. A detector unit for use in an open circuit electrical tire alarm system comprising a tube, a pair of resilient conducting elements received within the tube and a nouconducting solid heat-fusible plug, each conducting element having a free end, an inwardly constricted portion, a bowed portion and a contact arm, the solid heat-fusible plug separating the contact arms of the conducting elements and the resilient Contact arms being spaced apart within the tube at the inwardly constricted portion by an insulator, the conducting elements being arranged to cooperate with each other and with the inner surfaces of the tube in such in a manner that the conducting elements are compressed and urged into frictional engage ment with the inner surfaces of the tube to frictionally anchor the elements within the tube and to normally urge the contact arms to a closed position.

3. The detector unit of claim 2 wherein one contact arm contains -a contact point extending in the direction of the opposing contact arm.

4. The detector unit of claim 3 wherein the contact point is arranged on the contact arm at a point within the tube.

5. The detector unit of claim 2 wherein the portion of the contact arms bearing the heat-fusible plug extends beyond the edge of the tube.

6. A detector unit for use in an open circuit electrical re alarm system comprising a tube, a pair of resilient conducting elements received within the tube, a solid heat-fusible plug, and insulating means intermediate the plug and conducting elements, each conducting element having a free end, an inwardly constricted portion, a bowed portion and a contact arm, the solid heat-fusible plug separating the contact arms of the conducting elements and the resilient contact arms being spaced apart within the tube at the inwardly constricted portion by an insulator, the conducting elements being arranged to cooperate with each other and with the inner surfaces of the tube in such a manner that the conducting elements are compressed and urged into frictional engagement with the inner surfaces of the tube to frictionally anchor the elements within the tube and to normally urge the contact arms to a closed position.

References Cited in the 'rile of this patent UNITED STATES PATENTS 

